Phyllodes tumor of the breast is a rare neoplasm, particularly in adolescent girls and young women. It is usually presented as a unilateral palpable mass. We are reporting the case of an 11-year-old adolescent girl who came to our Diagnostical Imaging Department with non-hematic nipple discharge. Ultrasound, mammography, and magnetic resonance imaging were performed. The histological examination showed a phyllodes tumor. The management and the biological behavior of this uncommon tumor are discussed with particular regard to the very unusual clinical presentation in this patient.